JP-U-4-105906A shows a device for adjusting valve timing of the engine by utilizing the rotation torque of the motor. JP-11-324625A shows a device for adjusting a valve lift of the engine by utilizing the rotation torque of the motor.
In the valve opening-closing controller of such a motor utilizing type, a driving circuit for receiving a signal generated by a control circuit is used and electric conduction according to this receiving signal is executed with respect to the motor. For example, a method for separating a signal showing a target rotation number of the motor and a signal showing a target rotating direction of the motor and transmitting the signals from the control circuit to the driving circuit is conventionally considered. In accordance with such a method, information shown by each signal is limited to one. Therefore, the target rotation number shown by the former signal particularly becomes a high value in resolution. Since the resolution of the target rotation number becomes high in such a way, control accuracy of the valve opening and closing is improved.
However, when the signal showing the target rotation number and the signal showing the target rotating direction are separated, a signal line is required every each of these signals, which prevents a reduction in cost.